Chapter 3: What is important?


  • What are the key chapter elements (take home messages) that I should test you on?



  • What new things are you curious about and/or did not fully understand


  • This week, let’s focus on what it means to be human


The meaning of the term “humanism” has changed according to the successive intellectual movements that have identified with it. Generally, the term refers to a focus on human well-being and advocates for human freedom, autonomy, and progress. It views humanity as responsible for the promotion and development of individuals, espouses the equal and inherent dignity of all human beings, and emphasizes a concern for humans in relation to the world.

What are (at least three) key reasons this cartoon lacks accuracy and is deeply problematic?

Misconceptions about human evolution


Humans did not evolve from chimps, we both evolved from a common ancestor


Early human evolution was not a linear progression but a branching tree


Multiple species of ancient humans walked the earth, often at the same time


Modern humans originated in Africa and then spread around the world evolving incredible diversity (so the buff-white-male-endpoint is not only ridiculous but problematic in many ways)


There is no endpoint, humans are still evolving

Think Critically: Global Question…


What are the consequences of misconceptions about human evolution past, present & future?
















Is egocentrism at the root of the environmental crisis?

Human evolution fact and fallacies


  • Humans are a part of the tree of life, not above it
    • Aristotle and Scala Natura


  • Are humans the most complex organism on Earth?
    • octopus eye vs human eye


  • Nothing that exists on Earth is actually ‘primitive’
    • consider the basics of evolution and selection!



  • Why does this matter now?
    • stewardship not extraction
    • societies/cultures create false hierarchies based on ladder approach

Dangers of false hierarchies



Manufactured tiers within human species based on the ladder approach to evolution


A more perfect race of humans is developing/evolving (or can be created)


Used to uphold white supremacy, imperialism, colonialism, slavery and genocide


Used to create eugenics programs

Misconception: Trees not ladders!


Aristole (Scala Natura & Great Chain of Being) was wrong


Phylogenies do not imply that organisms are more advanced

Humans are the new kids on the block



  • Humans belong to a family of primates
    • group also contains chimps, gorillas and orangutans


  • Our genus (Homo) shares a common ancestor with chimps (Pan)
    • early ‘humans’ and Pan diverged 6-8mya


  • Our species (Homo sapien) evolutionary history is BRIEF

Whats in a name - Relatedness through taxonomy

Hominin tribe includes several genera, including Homo




  • Ancestral ‘humans’ can be split into ~4 groups (genera)


  • Groupings relate to timing and evolutionary milestones


  • Fossil record is very incomplete
    • common ancestor with Pan is unknown
    • total number of ancestral humans may change
    • Toumai fossil (Chad) dated 6-7 mya
    • Ardi fossil (Ethiopia) dated 4.4 mya

The Homo genus is all that is left

  • H.habilis was probably first (most primitive) → 2.3-1.4mya


  • H.sapiens evolved approx. 300,00 - 200,00 years ago


  • The evolution of the Homo genus was not a ladder!

Different species of Homo very likely interacted

Out of Africa and beyond


  • H. sapiens evolved on African continent
    • massive migration ~100,000 ya
    • not the first to leave


  • H. erectus probably left first
    • or H. egaster


  • H. neanderthalensis evolved in Europe/Asia


  • Our species left in a 2nd migration


  • Lots of debate!!

Different species of Homo may have interbred

  • Humans from outside Africa have traces of Neanderthal DNA
    • about 1–2% of their genomes
    • fossils suggest met in Middle East (~50,000 ya)


  • DNA from a 40,000-year-old human skeleton suggests a Neanderthal great-great grandparent


  • Denisovans lived across Asia, giving them opportunity to interbreed


  • Neanderthals and Denisovans likely interbred in Asia (~50,000ya)
    • Denisovans with immune-system genes from Neanderthals.

Is human evolution, dispersal, and climate related?

  • H. sapiens just about everywhere by 15,000ya
    • beyond other Homo spp.
    • Out competed other Homo spp.
  • Adapted to become ecological generalist/specialist
    • able to persist anywhere (generalist)
    • able to persist in extreme places (specialist)

Early Homo sapien migration altered the landscape


  • Humans have always been hunters


  • Human arrival associated with biodiversity loss
    • centered around larger animals
    • impacted whole ecosystems


  • Islands are great case studies
    • New Zealand, Madagascar


  • Humans not the only reason
    • related to big climate shifts

H.sapien population increased slowly until farming (11,000ya)

Why does this matter for global change?



  • Over human history…
    • Biomass of terrestrial vegetation has halved
    • More than 20% reduction in biodiversity
    • At least one million species threatened with extinction
    • More than 70% of the Earths land surface has been altered by humans
    • Total global biomass of wild animals today is < 25% of what it was during the Late Pleistocene
    • Terrestrial vertebrates biomass today is represented by livestock (59%) and living human beings (36%).